1. Field of the Invention
The present invention relates generally to a vibration apparatus and a method for controlling the same, and in particular, to a vibration apparatus for use in a mobile telecommunication terminal, for increasing the intensity of a vibration, and a method for controlling the same.
2. Description of the Related Art
In general, most mobile telecommunication terminals include a speaker for converting an electric signal into voice (sound) and a vibration device to generate vibration upon receipt of an incoming call.
FIG. 1 illustrates a structure of a common vibration device. Referring to FIG. 1, a common vibration device includes a magnet 1, a diaphragm 2, a vibration coil 3, a voice coil 4, a spring 5, and a housing 6. When current flows in the vibration coil 3, an electric field is generated. The electric field moves the magnet 1 in cooperation with a magnetic field of the magnet 1. FIG. 2 illustrates the movement of the magnet 1. The repeated movement of the magnet 1 generates induced current in the voice coil 4. As a result, the diaphragm 2 connected to the voice coil 4 vibrates. As the direction of the current supplied to the vibration coil 4 changes more frequently, the magnet 1 moves faster.
A resonance frequency driving the vibration device is determined in the manufacturing process of the mobile telecommunication terminal (hereinafter, referred to “mobile terminal” for short) on the basis of the resonance points of the vibration device and the entire mobile terminal with the vibration device. The resonance points of the vibration device and the entire mobile terminal are determined by the material and the weight of the mobile terminal and the way of carrying the mobile terminal. The resonance frequency can be changed due to a physical shock caused by falling or a change in the weight of the mobile terminal with the vibration device.
For example, a mobile terminal indicating receipt of an incoming call by generating vibration is manufactured to be relatively small in size so that it can be carried in various ways. For example, the mobile terminal can be worn about the neck of a user, held in one hand of the user, or put into the pocket or the bag of the user. The resonance frequency of the entire mobile terminal with the vibration device varies according to the way of carrying the mobile terminal. Also, the resonance frequency changes according to the weight of the battery mounted on the mobile terminal.
FIG. 3 illustrates a change in the intensity of vibration according to a change in the weight of the mobile terminal with the vibration device. Referring to FIG. 3, the mobile terminals having the weights of 80 g, 100 g and 120 g have their maximum vibration intensities at the resonant frequencies of 183 Hz, 181 Hz and 180 Hz, respectively.
The vibration device is driven by a driving signal, a resonance frequency of which is determined in the manufacturing process of the mobile terminal with the vibration device. Therefore, it is not possible to cope with the change in the resonance frequency at which the maximum vibration intensity occurs, due to the aging of the mobile terminal, the physical shock, and the change in the weight.